The study by researchers at Brown University and Tufts University found that snacks improve diet quality in elementary school children but detract from diet quality in adolescents.
While snacks uniformly contribute to energy intake in both children and adolescents, the effect of snacking on dietary quality differs by age group, researchers said.
The diet quality differences by age found in the study were significant. Among the 92 school-age children aged 9 to 11 in the study, each snack raised their diet quality by 2.31 points, as measured on the Healthy Eating Index, 2005, developed by the US Department of Agriculture.
Among the 84 teens in the study, aged 12 to 15, each snack dragged the quality score down by 2.73 points, while each meal increased the quality score by 5.40 points.
Overall, each snack contributed about half as much to total daily energy intake as each meal, making them high-stakes eating moments, said study first author E Whitney Evans, a postdoctoral research fellow at Brown University and the Weight Control and Diabetes Center at The Miriam Hospital.
To conduct the study, Evans and a team of registered dietitians asked kids (with parental consent) at four Boston-area schools to provide some basic demographic information.
Then, on two separate occasions, the kids completed a 24-hour diet recall, in which they recounted what they ate during the previous day.
Researchers, including senior author Aviva Must, professor and chair of the Department of Public Health and Community Medicine at Tufts University School of Medicine, determined the number of meals and snacks reported by each child, along with their total energy intake and diet quality score.
The study does not explain why snacking has opposite effects on diet quality depending on a child's age, but the researchers noted that younger children more frequently depend on (and perhaps abide) grownups, while older kids are more often making their own snacking choices.
The findings are published in the journal Public Health Nutrition.